Tarago River

The Tarago River rises in the Tarago State Forest and flows into the Tarago Reservoir at Neerim, which sits in the upper reaches of the Tarago River and harvests inflow from all upstream tributaries. Downstream of the reservoir, the river flows close to the town of Rokeby before meeting the Bunyip River (of which it is a major tributary) at Longwarry North. From there, the Bunyip River flows through a modified, straightened channel — Bunyip Main Drain — to flow into Western Port. This downstream reach supplies many irrigators in the catchment.

The Tarago River continues to be an important place for Traditional Owners and their Nations. The Registered Aboriginal Parties (RAP) covering small sections of the Tarago catchment are the Bunurong Land Council Aboriginal Corporation and the Gunaikurnai Land and Waters Aboriginal Corporation.

System map

Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches can receive environmental water.

Environmental watering objectives in the Tarago River

Improve health and increase diversity of native riverside vegetation

Protect and increase native fish populations including threatened species (the Australian grayling and river blackfish) by providing habitat and triggers for fish to migrate and spawn

Maintain and improve habitat availability for macroinvertebrates Provide habitat and food for waterbugs

Maintain and improve foraging habitat for platypus

Environmental values

The Tarago system contains several significant and threatened native plant and animal species including the Australian grayling, long pink-bells, tree geebung and swamp bush-pea. The upper catchment has healthy riparian vegetation and highly diverse in-stream habitat that supports native fish including river blackfish and mountain galaxias. While the lower catchment has been highly modified, it contains patches of remnant vegetation and healthy populations of Australian grayling and platypus.

Social and economic values

There are several reserves, picnic areas and designated fishing locations along the length of the Tarago system as well as a popular caravan park and public land in the headwaters. These all contribute to the social and recreational value of the Bunyip and Tarago rivers. Many irrigators rely on water from the Tarago system and the reservoir also supplies some urban demand.

Conditions 2018

Conditions were generally drier and warmer than average in 2017–18, but the catchment also had high rainfall in September and December 2017.

The current environmental flow recommendations for the Tarago River include a high flow in spring to inundate barriers to allow fish movement within and between reaches. The recommended spring high flow did not occur in 2017–18 (either naturally or through releases of water for the environment), but monitoring demonstrated that fish are moving through the system at lower flows. This knowledge will be incorporated into the revised FLOWS assessment for the river, which is being currently undertaken.

Water for the environment was used in the drier, summer months — February 2018 had much-lower-than-average rainfall — to provide freshening flows to maintain water quality. An autumn high flow was delivered in May 2018 to trigger the downstream dispersal and spawning of Australian grayling.

Scope of environmental planning

Table 1.
Potential environmental watering actions and objectives for the Tarago River

Potential
environmental watering

Environmental
objectives

Summer/autumn freshes (up to 5 freshes of 75–100 ML/day for 2–4 days each in December–May)

Maintain water quality and provide habitat for river blackfish, Australian grayling, platypus and waterbugs

1 Winter/spring low flows are unlikely to be delivered as the volume required would severely affect the ability to provide other environmental flow events..

2 Summer/autumn low flows are generally provided by passing flows under the environmental entitlement but during dry conditions it may be necessary to supplement these flows using managed water for the environment.

Risk management

In preparing its seasonal watering proposal, Melbourne
Water considered and assessed the risks of environmental
watering and identified mitigation strategies. Program
partners continually reassess risks and mitigation actions
throughout the water year

Engagement

Table 2 shows the partners and stakeholder organisations with which Melbourne Water engaged when preparing the Tarago system seasonal watering proposal.

Seasonal watering proposals are informed by longer-term regional catchment strategies, regional waterway strategies, environmental flow studies, water management plans and other studies. These incorporate a range of environmental, cultural, social and economic perspectives and longerterm integrated catchment and waterway management objectives. For further details, refer to the Port Phillip and Western Port Regional Catchment Strategy and Melbourne Water's Healthy Waterways Strategy.